Bioinformatics tools, immunohistochemistry techniques, and statistical analyses were employed to evaluate IDO1 expression levels and their association with clinical pathological features and prognosis in patients with lung adenocarcinoma.<h4>Results</h4>IDO1 was found to be significantly overexpressed in various types of tumors, with higher levels correlating with poorer progression-free survival (PFS) and overall survival (OS). This evidence concerns the gene IDO1 and lung adenocarcinoma.